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Abstract:

A stereoscopic image display device includes a liquid crystal panel
section, a light source section, a light detection section, a light
source control section, a shutter glasses section, and a timing
generation section generating a light emission drive signal, a light
detection gate signal, and shutter switching signals in synchronization
with an image synchronization signal. The timing generation section,
generates the light emission drive signal which causes each of the
regions of the light source section to emit light in accordance with
scanning performed in the liquid crystal panel section, and which causes
all the regions of the light source section to emit light in a
predetermined period, and generates the light detection gate signal which
enables detection of the light detection section in the predetermined
period, and generates the shutter switching signals for switching left
and right shutters to a non-transmissive mode.

Claims:

1. A stereoscopic image display device, comprising: a liquid crystal
panel section in which successive scanning is performed in a
predetermined direction in synchronization with an image signal, so that
transmittance of light is varied in accordance with a gray scale level of
said image signal; a light source section being divided into a plurality
of regions; a light detection section detecting light emission intensity
of said light source section; a light source control section controlling
the light emission intensity of said light source section based on a
light detection value detected by said light detection section; a shutter
glasses section having left and right shutters, said shutter glasses
section switching said left and right shutters between a transmissive
mode and a non-transmissive mode; and a timing generation section
generating, in synchronization with an image synchronization signal, a
light emission drive signal causing said light source section to emit
light, a light detection gate signal causing said light detection section
to detect the light emission intensity of said light source section, and
a shutter switching signal for causing said left and right shutters to
switch between the transmissive mode and the non-transmissive mode,
wherein said timing generation section generates said light emission
drive signal which causes each of said regions of said light source
section to emit light in accordance with said scanning performed in said
liquid crystal panel section, and which causes all the regions of said
light source section to emit light in a predetermined period, and
generates said light detection gate signal which enables detection of
said light detection section in said predetermined period, and generates
said shutter switching signal for switching said left and right shutters
to the non-transmissive mode.

2. The stereoscopic image display device according to claim 1, wherein
said timing generation section generates said light emission drive signal
with reference to an image valid signal, in place of said image
synchronization signal.

3. The stereoscopic image display device according to claim 1, further
comprising a light guide section outputting light received from said
light source section to said liquid crystal panel section, wherein said
light detection section is installed between said light guide section and
said liquid crystal panel section.

4. The stereoscopic image display device according to claim 1, wherein
said image signal is a signal having a black image inserted between a
left-eye dedicated image and a right-eye dedicated image both being
converted with a doubled frame frequency.

5. The stereoscopic image display device according to claim 1, wherein
said image signal is a signal having an identical image successively
inserted twice to a left-eye dedicated image and a right-eye dedicated
image both being converted with a doubled frame frequency.

6. The stereoscopic image display device according to claim 1, wherein
said timing generation section generates said light emission drive
signal, said light detection gate signal, and said shutter switching
signal, for each predetermined cycle being longer than one frame of said
image signal.

7. The stereoscopic image display device according to claim 1, wherein
said light source control section controls the light emission intensity
of said light source section, based on said light detection value
detected by said light detection section and a reference light detection
value set previously, and said reference light detection value reduces in
accordance with a light emission accumulation time of said light source
section.

8. The stereoscopic image display device according to claim 1, wherein
said light source control section controls the light emission intensity
of said light source section, based on said light detection value
detected by said light detection section and a reference light detection
value set previously, and a reference light emission intensity value,
which is an initial value of the light emission intensity of said light
source section, is set for each of conditions including temperature of
said light source section and a light emission accumulation time of said
light source section.

9. The stereoscopic image display device according to claim 1, wherein
said light source control section records and retains a light emission
intensity value obtained when said light source section is turned off,
said light emission intensity value being used as an initial value of the
light emission intensity of said light source section for next emission
of light.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a stereoscopic image display
device which displays a right-eye dedicated image and a left-eye
dedicated image on a liquid crystal panel in a time-sharing manner, and
which displays a stereoscopic image separating the right-eye dedicated
image and the left-eye dedicated image from each other through use of
shutters.

[0003] 2. Description of the Background Art

[0004] In recent years, as an image displaying technique for allowing the
user to virtually experience stereoscopic viewing, the stereoscopic image
displaying technique using parallax between the eyes is known. As such a
stereoscopic image displaying technique, the following scheme is
proposed. A left-eye dedicated image and a right-eye dedicated image are
temporally alternatively displayed on a display device. At the same time,
in synchronization with the timing at which the images are switched, the
right and left field of views are temporally separated from each other
through use of shutter glasses, which shut the right and left field of
views, respectively. Thus, the right-eye dedicated image and the left-eye
dedicated image are presented to the right and left eyes of the user,
respectively.

[0005] Such a stereoscopic image display device involves problem of 3D
crosstalk, i.e., the left-eye dedicated image not intended to be incident
upon the right eye of the user is incident upon the right eye, or the
right-eye dedicated image not intended to be incident upon the left eye
is incident upon the left eye.

[0006] Further, such a stereoscopic image display device involves another
problem. That is, the luminance and white color of the light source used
as the backlight, which emits light on the back side of the liquid
crystal panel, change because of variations in temperature and aging.

[0007] Addressing such problems, a liquid crystal display device of
Japanese Patent Application Laid-Open No. 11-295689 (1999) discloses a
technique of employing three types of backlight differing from one
another in illumination colors and optical sensors corresponding to the
illumination colors, to thereby achieve the operation in which the
illumination colors are always equal to set values, despite the
variations in temperature and aging of the backlight.

[0008] A stereoscopic video display device of Japanese Patent Application
Laid-Open No. 2010-276928 discloses a technique of suppressing 3D
crosstalk by allowing scanning to be performed with divided backlights in
synchronization with a video image such that the backlights are
successively lit up for short periods (backlight scanning).

[0009] However, in an attempt to solve the two problems noted above at the
same time, when the backlight sources of different illumination colors
are used as in the liquid crystal display device of Japanese Patent
Application Laid-Open No. 11-295689 (1999), and control is exerted to
perform scanning with the divided backlight sources in synchronization
with an image such that light is successively emitted for short periods
as in the stereoscopic video display device of Japanese Patent
Application Laid-Open No. 2010-276928, the optical sensors will be
affected by the light amount of adjacent backlight sources. Thus, it
invites problem of the output values of the optical sensors not becoming
constant. Accordingly, it is difficult to maintain the illumination
colors of the backlight sources to be constant against variations in
temperature and aging of the backlight sources.

SUMMARY OF THE INVENTION

[0010] An object of the present invention is to provide a stereoscopic
image display device being capable of maintaining the illumination colors
of a light source section to be constant against variations in
temperature and aging of the light source section and being capable of
suppressing 3D crosstalk, through use of the light source section being
divided into a plurality of regions.

[0011] A stereoscopic image display device of the present invention
includes a liquid crystal panel section in which successive scanning is
performed in a predetermined direction in synchronization with an image
signal, so that transmittance of light is varied in accordance with a
gray scale level of the image signal; a light source section being
divided into a plurality of regions; a light detection section detecting
light emission intensity of the light source section; a light source
control section controlling the light emission intensity of the light
source section based on a light detection value detected by the light
detection section; a shutter glasses section having left and right
shutters, the shutter glasses section switching the left and right
shutters between a transmissive mode and a non-transmissive mode; and a
timing generation section generating, in synchronization with an image
synchronization signal, a light emission drive signal causing the light
source section to emit light, a light detection gate signal causing the
light detection section to detect the light emission intensity of the
light source section, and a shutter switching signal for causing the left
and right shutters to switch between the transmissive mode and the
non-transmissive mode. The timing generation section, generates the light
emission drive signal which causes each of the regions of the light
source section to emit light in accordance with the scanning performed in
the liquid crystal panel section, and which causes all the regions of the
light source section to emit light in a predetermined period, and
generates the light detection gate signal which enables detection of the
light detection section in the predetermined period, and generates and
the shutter switching signal for switching the left and right shutters to
the non-transmissive mode.

[0012] According to the present invention, the timing generation section
generates the light emission drive signal which causes all the regions of
the light source section to emit light in a predetermined period and the
light detection gate signal which enables detection of the light
detection section. Therefore, the light detection section can perform
detection in the state where all the regions of the light source section
are caused to emit light at the same time. Therefore, the light detection
section can perform stable detection of the light detection value with
small errors, without being affected by the amount of light of adjacent
regions in the light source section. Since the light source control
section controls the light emission intensity of the light source section
based on the light detection value with small errors, the illumination
color of the light source section can be maintained to be constant
against variations in temperature and aging of the light source section.

[0013] Further, the timing generation section generates the shutter
switching signal for switching the left and right shutters to the
non-transmissive mode in the predetermined period. Therefore, by
switching the left and right shutters to the non-transmissive mode in the
period where all the regions of the light source section are caused to
emit light at the same time, it becomes possible to suppress occurrence
of 3D crosstalk attributed to the light emission of the light source
section.

[0014] These and other objects, features, aspects and advantages of the
present invention will become more apparent from the following detailed
description of the present invention when taken in conjunction with the
accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a block diagram of a stereoscopic image display device
according to a first preferred embodiment;

[0016] FIG. 2 is a diagram showing the installation state of a light guide
section, a light source section, and a light detection section on the
back side of a liquid crystal panel section;

[0017] FIG. 3 is a timing chart showing the operation of an image
converting section;

[0018] FIG. 4 is a timing chart showing the relationship between the
response of liquid crystal to an image signal and a light emission drive
signal;

[0022] FIG. 8 is a timing chart showing light detection and shutter
switching control exerted in a stereoscopic image display device
according to a second preferred embodiment; and

[0023] FIG. 9 is a timing chart showing light detection and shutter
switching control exerted in a stereoscopic image display device
according to a third preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Preferred Embodiment

[0024] A description will be given of a first preferred embodiment of the
present invention with reference to the drawings. FIG. 1 is a block
diagram of a stereoscopic image display device according to the first
preferred embodiment of the present invention. As shown in FIG. 1, the
stereoscopic image display device includes an image converting section 1,
a timing generation section 2, a reference value recording section 3, a
light detection section 4, a light source control section 5, a light
source section 6, a light guide section 7, a liquid crystal panel section
8, and a shutter glasses section 9.

[0025] Next, a description will be given of constituent elements. As shown
in FIG. 3, it is understood that an image signal I1 input to the image
converting section 1 is an image in which a left eye image L and a right
eye image R are sorted to form a pair of left eye image and right eye
image in a time-sharing manner. Further, the description will be given
based on that one image frame time of the left eye or the right eye is T.

[0026] As shown in FIGS. 1 and 3, the image converting section 1 converts
the image signal I1 such that the frame frequency is doubled, and inserts
one black image between a left eye image L' and a right eye image R', to
generate an image signal I2. That is, the one image frame time of the
image signal I2 for the left or right eye becomes T/2. Further, the image
converting section 1 outputs an image synchronization signal V indicative
of the head timing of the left eye image L' and that of the right eye
image R' synchronized with the image signal I2 to the timing generation
section 2.

[0027] As shown in FIG. 1, the timing generation section 2 generates a
light emission drive signal Pn of the light source section 6 based on the
image synchronization signal V output from the image converting section 1
and the number of vertical division n of the light source section 6, and
outputs the generated light emission drive signal Pn to the light source
section 6. Further, the timing generation section 2 generates a light
detection gate signal GE and outputs the same to the light detection
section 4. Further, the timing generation section 2 generates shutter
switching signals SL, SR, and outputs the same to the shutter glasses
section 9. Here, the light emission drive signal Pn is output as many as
the number of vertical division n, and the light detection gate signal GE
is output as many as the number of optical sensors (not shown) of the
light detection section 4.

[0028] The reference value recording section 3 records and retains a
reference light detection value MD and a reference light emission
intensity value ME, which are set previously by the user. The reference
light detection value MD exists as many as the number of combination of
the number of installed optical sensors of the light detection section 4
and the colors of the sensors, and the reference light emission intensity
value ME exists as many as the number of combination of the number of
divided regions of light source section 6 and the number of colors.

[0029] In connection with the scheme of determining the reference light
detection value MD and the reference light emission intensity value ME,
the output light from the liquid crystal panel section 8 or the output
light from the shutter glasses section 9 upon receipt of a reference
signal, e.g., a full white signal, is measured by a luminance meter being
externally installed, and the light emission intensity value of each
color of the light source section 6 is adjusted such that the output
light achieves the targeted luminance, white balance, color temperature
and the like.

[0030] Further, the light emission intensity value of each of the divided
regions of the light source section 6 is adjusted, such that the
variations in luminance and color of the liquid crystal panel section 8
become uniform. In this manner, the reference value recording section 3
records and retains the light detection value of each optical sensor,
which is obtained at the time when the output light from the liquid
crystal panel section 8 and the output light from the shutter glasses
section 9 are adjusted to the targeted value, as the reference light
detection value MD. Further, the reference value recording section 3
records and retains the light emission intensity value being input to
each of the divided regions of the light source section 6 as the
reference light emission intensity value ME.

[0031] The light detection section 4 includes, in the light source section
6, a plurality of optical sensors capable of detecting light emission
intensity of at least one color, to perform light detection in High
period of the light detection gate signal GE output from the timing
generation section 2, and outputs a light detection value D. The light
detection section 4 outputs, as the light detection value D, a voltage
value being proportional to the light emission intensity, for example.

[0032] Further, the light detection section 4 may be one luminance sensor
capable of detecting a luminance value, or may be color sensors of three
colors, namely, red (R), green (G), and blue (B). The type of such
sensors is not limited, and may be, for example, a photocell, a
photodiode, or a combination of such optical filters. With multicolor
optical sensors, the light detection value D is output as many as the
number of colors.

[0033] The light source control section 5 outputs, for the first time
immediately after being activated, the reference light emission intensity
value ME recorded in the reference value recording section 3 to the light
source section 6. From the second time onward, the light source control
section 5 determines a light emission intensity value E such that the
light detection value D output from the light detection section 4 and the
reference light detection value MD become equal to each other, and
outputs the determined light emission intensity value E to the light
source section 6. Here, the light emission intensity value E is the
current amount, for example. It is understood that the light amount
increases in proportional to the light emission intensity value E when
the light emission intensity value E is input to the light source section
6.

[0034] Specifically, when the light detection value D is smaller than the
reference light detection value MD, the light source control section 5
increases the light emission intensity value E such that the light
detection value D and the reference light detection value MD become equal
to each other and outputs the same. On the other hand, when the light
detection value D is greater than the reference light detection value MD,
the light source control section 5 reduces the light emission intensity
value E such that the light detection value D and the reference light
detection value MD become equal to each other and outputs the same. In
this manner, by the light source control section 5 operating to equalize
the light detection value D and the reference light detection value MD,
the light emission intensity of the output light achieves the targeted
value. Note that the light emission intensity value E is output from the
light source control section 5 as many as the number of divided regions
of the light source section 6.

[0035] The light source section 6 is divided into a plurality of regions
in the vertical direction of the liquid crystal panel section 8. That is,
the light source section 6 is divided by n (n≧2) so as to be
divided into at least the top portion region and the bottom portion
region. Further, the light source section 6 is structured with the light
source of at least one color. Still further, the light source section 6
is the light source which emits pulsed light at the light emission
intensity value E output from the light source control section 5 in High
period of the light emission drive signal Pn output from the timing
generation section 2. Here, the outline arrows in FIG. 1 each represent
light.

[0036] The light source section 6 may produce white light by blending
light through use of a combination of multicolor light sources, e.g., a
combination of three color light sources of red (R), green (G), and blue
(B), or a combination of two color light sources of cyan (C) and red (R).
Any element can be used as the light emitting element of each light
source, e.g., a light emitting diode (LED), laser, an organic
electroluminescence (organic EL) or the like, or combinations thereof. It
is understood that the light source section 6 is capable of controlling
the divided light sources (regions) independently of one another. The
light source section 6 may be installed immediately below the liquid
crystal panel section 8, or may be installed right and left ends and top
and bottom ends of the liquid crystal panel section 8.

[0037] The light source section 6 performs pulsed light emission based on
the light emission drive signal Pn. Further, the light source section 6
is capable of changing the light emission intensity depending on the
light emission intensity value E. The light emission drive signal Pn
exists as many as the number of vertical division n. The light source
section 6 emits light in High period of the light emission drive signal
Pn, and the light emission intensity is set by the light emission
intensity value E. Further, the light source section 6 is turned off in
Low period. The light emission intensity value E may be: the number of
combination of the number of vertical division n and the number of light
source color m; or the number of light source color m. Alternatively, it
may be the number of vertical division n, or may be just one.

[0038] The light guide section 7 outputs light, which has been received
from the light source section 6, to a predetermined region of the liquid
crystal panel section 8. The light evenly diffuses on the incident
surface of the liquid crystal panel section 8, whereby the area light
source is achieved. Further, the light guide section 7 also has the
function of producing white color by blending light from the light source
section 6 which employs a combination of multicolor light sources, e.g.,
red (R), green (G), and blue (B). Still further, the light guide section
7 may be structured to cause the light diffusion entirely with one light
guide plate, even when the light source section 6 is divided into n
regions.

[0039] The liquid crystal panel section 8 is, for example, a transmissive
liquid crystal panel in which the color filters are arranged. In the
liquid crystal panel section 8, successive scanning is performed from top
to bottom in synchronization with the image signal I2 output from the
image converting section 1. Then, as the timing generation section 2
causes each region of the light source section 6 to emit light in
accordance with the scanning in the liquid crystal panel section 8, the
liquid crystal panel section 8 displays an image by varying the
transmittance of the light from the back side for each pixel in
accordance with the gray scale level of the image signal I2.

[0040] The shutter glasses section 9 has a left eye shutter (not shown)
and a right eye shutter (not shown), and switches the left and right eye
shutters between a transmissive mode and a non-transmissive mode in
accordance with the shutter switching signals SL, SR output from the
timing generation section 2.

[0041] Here, the left-eye dedicated shutter switching signal is denoted by
SL and the right-eye dedicated shutter switching signal is denoted by SR.
The shutter switching signals SL, SR allow an image to be transmissive
based on that the shutter being open in High period, and allows an image
to be non-transmissive based on that the shutter being closed in Low
period. Allowing the user to look an image displayed on the liquid
crystal panel section 8 while showing only the left eye image to the left
eye and only the right eye image to the right eye through use of the
shutter glasses section 9, the user can observe the image as a
stereoscopic image.

[0042] Note that the shutters switching the image between the transmissive
mode and the non-transmissive mode can be structured in any manner. For
example, it may be structured based on the combination of a polarizing
plate and liquid crystal switching its polarizing direction, such that
the transmissive mode is set when the polarizing angle is in an identical
direction, and that the non-transmissive mode is set when the polarizing
angle is in the closing direction. Alternatively, it may be structured to
physically close. Further, any method may be employed for transmitting
the shutter switching signals SL, SR, e.g., infrared rays, radio waves,
wired transmission or the like.

[0043] Next, a description will be given of the installation of the light
guide section 7, the light source section 6, and the light detection
section 4. FIG. 2 is a diagram showing the installation state of the
light guide section 7, the light source section 6, and the light
detection section 4 on the back side of the liquid crystal panel section
8. On the back side of the liquid crystal panel section 8, a light guide
plate of the light guide section 7 is installed. The light source section
6 is installed at the left end of the light guide plate. The light source
section 6 includes n regions provided in the vertical direction, the
regions being capable of being controlled independently of one another.

[0044] The light emitted by the light source section 6 is diffused across
the surface by the light guide section 7, and guided to the right end of
the liquid crystal panel section 8. The light detection section 4 detects
the light emission intensity of the diffused light. The light guide
section 7 has the function of diffusing light across a considerably wide
surface without unevenness. Therefore, it is not only each range
indicated by the dashed lines in FIG. 2 that lights up. Instead, the
resultant light amount is the overlapped light from the adjacent light
sources or from all the light sources being considerably away from one
another. Note that the light detection section 4 may be provided at an
arbitrarily position between the light guide section 7 and the liquid
crystal panel section 8. Further, the light detection section 4 may be
installed in one place or in a plurality of places. In the case where the
light detection section 4 is installed in each of a plurality of places,
the light detection control is exerted by associating the light detection
section with each of the divided regions of the light source section 6.

[0045] Next, with reference to FIG. 3, a detailed description will be
given of the operation of the image converting section 1. FIG. 3 is the
timing chart showing the operation of the image converting section 1. As
shown in FIG. 3, the image converting section 1 converts the image signal
I1 such that the frame frequency is doubled, and inserts one black image
between the left eye image L' and the right eye image R' to generate the
image signal I2. The generated image signal I2 is output to the liquid
crystal panel section 8.

[0046] In the case where the image signal I1 is input in order of L1, R1 .
. . with one image frame period (cycle) T, the output image signal I2 is
converted such that the frame frequency is doubled, and thereafter
converted to achieve the order of L1', black, R1', black . . . with one
image frame period T/2. This black image is inserted for the purpose of
separating the left eye image and the right eye image from each other.
Further, the image converting section 1 outputs the image synchronization
signal V indicative of the head timing of the left eye image L' and that
of the right eye image R' being synchronized with the image signal I2 to
the timing generation section 2. Here, the pulse width of the image
synchronization signal V may be an arbitrary width, because the rising of
the image synchronization signal V is used as the reference.

[0047] The image signal I2 output from the image converting section 1 is
input to the liquid crystal panel section 8. In the liquid crystal panel
section 8, successive scanning is performed from top to bottom in
synchronization with the image signal I2, to vary the transmittance. That
is, the variation begins at different times between the top portion and
bottom portion of the liquid crystal panel section 8. Further, the liquid
crystal is slow in responding by varying the transmittance, and the
liquid crystal responds such that the targeted transmittance is gradually
achieved. Here, the transmittance appears as gray scale levels.

[0048] Next, with reference to FIG. 4, a description will be given of the
relationship between the response of liquid crystal to the image signal
I2 and the light emission drive signal Pn. FIG. 4 is a timing chart
showing the relationship between the response of liquid crystal to the
image signal I2 and the light emission drive signal Pn. Here, it is
understood that the light source section 6 is divided into n regions in
the vertical direction of the liquid crystal panel section 8 and that the
divided regions are capable of being controlled independently of one
another. Similarly, in the case where the light source section 6 is
divided into a plurality of regions also in the horizontal direction of
the liquid crystal panel section 8, control is exerted for each of those
regions divided in the vertical direction. For the sake of convenience,
it is understood that, in the image signal I2 being input to the liquid
crystal panel section 8, both the left eye image L' and the right eye
image R' are full white images.

[0049] In FIG. 4, the horizontal axis indicates time, and each wavy line
indicates the response of liquid crystal. When the wavy line rises, the
transmittance increases; when the wavy line lowers, the transmittance
reduces. Point A1 is the point where the write operation of the left eye
image L' corresponding to the area near the topmost portion of the liquid
crystal panel section 8 is performed with the gray scale level. The
liquid crystal begins gradually responding by white being written, and
the transmittance increases. Point B1 is the point where the write
operation of the black image, which is the next frame, is performed. By
black being written, the transmittance of the liquid crystal gradually
reduces. It can be seen that the point immediately before point B1 is the
point where an adequate response time has elapsed, and where the
substantially targeted transmittance corresponding to the left eye image
L' is achieved. This is the example where the response of liquid crystal
is slow. In the case where the response of liquid crystal is fast enough,
the response converges prior to that point and the transmittance becomes
constant. That is, it can be seen that it is optimum to cause the light
source section 6 to emit light with reference to point B1.

[0050] On the other hand, point An is the point where the write operation
of the left eye image L' corresponding to the bottommost portion of the
liquid crystal panel section 8 is performed with the gray scale level.
Point An is shifted rightward in accordance with the lapse of time from
point A1. Point Bn is the point where the write operation of the black
image at the bottommost portion of the liquid crystal panel section 8 is
performed. It can be seen that, at the bottommost portion of the liquid
crystal panel section 8 also, the point immediately before point Bn is
the point where the substantially targeted transmittance corresponding to
the left eye image L' is achieved.

[0051] In this manner, it is optimum to cause the light source section 6
to emit light with reference to the area near points B1, B2, Bn. That is,
it is desirable that the light source section 6 is controlled to emit
light while successively shifting in accordance with the number of
vertical division n, such that the light source section 6 emits light
immediately before a change takes place in the next frame, in
synchronization with the scan timing of the image.

[0052] Each solid line represents the light emission drive signal Pn of
the light source section 6. The light emission drive signal Pn is
successively shifted employing the area near points B1, B2, Bn as the
reference of falling, to cause the light source section 6 to emit light.
Here, the light emission drive signal Pn of the light source section 6
shows that Low level turns off the light source section 6 and High level
causes the light source section 6 to emit light. The shift amount is
determined by the cycle of the image synchronization signal V and the
number of vertical division n of the light source section 6.

[0053] Next, with reference to FIG. 5, a description will be given of the
timing of generating the light emission drive signal Pn. FIG. 5 is an
exemplary timing chart showing the timing of generating the light
emission drive signal Pn. The image synchronization signal V indicates
the head timing of the left eye image L' and that of the right eye image
R' being in synchronization with the image signal I2. The cycle of the
image synchronization signal V is T. In connection with the light
emission drive signal in FIG. 5, the wavy line represents the response of
liquid crystal, while the solid line represents the light emission drive
signal Pn of the light source section 6. For the sake of convenience, the
description will be given of the case where the number of vertical
division n of the light source section 6 is 4.

[0054] By employing the area near point Bn shown in FIG. 4 as the light
emitting period of the light source section 6, the optimum light emission
timing with which the response of liquid crystal is considered is
achieved. That is, it is designed such that the falling point of the
light emission drive signal Pn is in the area near point Bn. The shift
amount S of the light emission drive signal Pn is determined by the cycle
T of the image synchronization signal V and the number of vertical
division n of the light source section 6, which is expressed by the
following equation:

S=T/2n

[0055] When T/2 period has elapsed since the rising of the image
synchronization signal V, the timing generation section 2 causes the
first light emission drive signal P1 to fall, to generate the light
emission drive signal Pn as being time-shifted by the shift amount S. For
example, with the light source section 6 with four divided regions, the
falling point of the light emission drive signal P1 is point T/2, and the
falling point of the light emission drive signal P2 is point T/2+T/8.

[0056] High period of the light emission drive signal Pn is the light
emitting period of the light source section 6. When the luminance is to
be increased, only the rising timing is changed while the falling timing
is unchanged, to thereby increase High period. In this manner, luminance
is adjusted with the falling timing of the light emission drive signal Pn
being fixed and the rising timing being adjusted. This rising timing
adjustment is represented by double-headed arrows.

[0057] The image signal I2 is a signal in which the black image for one
screen is inserted between the left eye image L' and the right eye image
R', which have undergone conversion with the doubled frame frequency.
Accordingly, since it is not necessary to display this black image, and
in order to suppress 3D crosstalk being the transition state of making a
response, the light source section 6 is turned off for this period. That
is, control should be exerted such that light is emitted by 50% of cycle
T or less than that. Note that, as the light emitting period is shorter,
3D crosstalk can more be suppressed.

[0058] In the case where the number of vertical division of the light
source section 6 is small, since each of the divided regions of the light
source section 6 has much width, the scan timing of the liquid crystal
panel section 8 is different between the top portion and bottom portion
of the divided light source section 6. For example, when the number of
vertical division n is 4, the width is 1/4 as great as the period of the
vertical scanning.

[0059] Accordingly, as shown in FIG. 6, the phases of the light emission
drive signals P1 to P4 may be uniformly delayed taking into consideration
of the image scan start time at the center of the width of th light
source section 6. That is, though the light emission drive signal is
generated based on that P1 is the scan start point of the vertical
topmost portion in FIG. 5, in FIG. 6, the phases are uniformly delayed
based on that the scan start point of P1 is 1/8 period, which corresponds
to half of the 1/4 period of the vertical scanning.

[0060] Further, though it has been described that the position of the
image beginning to change to be the black image is the falling of the
light emission drive signal P1, the position may be slightly delayed from
the position of the image beginning to change to be the black image, and
the phases of the light emission drive signals P1 to P4 may be uniformly
delayed such that peak of the response of liquid crystal is included in
the light emitting period. In this manner, the phase of the light
emission drive signal Pn is structured to be adjustable.

[0061] In this manner, by successively turning on the divided regions of
the light source section 6 in synchronization with scanning of the image,
the light emission timing of the light source section 6 corresponding to
the response of liquid crystal can be optimized both at the top portion
or bottom portion of the liquid crystal panel section 8, and 3D crosstalk
can be suppressed.

[0062] In connection with the light emitting element such as laser or LED,
the light emission intensity may change by the variations in temperature
and aging of the element.

[0063] Further, such a light emitting element itself individually varies
in the light emission amount. Therefore, the color balance of the light
source may change and unintended coloring or unevenness in color may
appear in the displayed image. Accordingly, the light detection section 4
is provided for adjusting the light emission intensity of the light
source section 6, and the timing generation section 2 generates the light
detection gate signal GE for enabling detection of the light detection
section 4.

[0064] It is the optimum to carry out this light detection at the timing
where the divided regions of the light source section 6 are turned on at
the same time. In the case where the light detection is simply carried
out with the light detection gate signal GE whose timing is identical to
the light emitting period, and where the light source section 6 is
vertically divided and control is exerted such that the light emission
timing is time-shifted, there is no timing at which all the regions of
the light source section 6 emit light at the same time. Furthermore,
since the light is diffused by the light guide plate, there is problem
that the light detection amount does not become constant as being
affected by the divided regions of the light source section 6 surrounding
the installed optical sensors.

[0065] For example, in FIG. 5, in the case where the light detection is
carried out for all the regions of the light source section 6 at the
timing identical to P1, the region driven at P2, which is adjacent to the
region driven at P1, emits light at the later stage of the light emission
timing of P1. Therefore, the light detection amount does not become
constant. Further, when the user increases or reduces the luminance of
the light source section 6, the length of the light emitting period is
controlled. Therefore, the degree of overlap of light in adjacent regions
of the light source section 6 varies, and hence the light detection
amount does not become constant. For example, when the user reduces the
luminance of the light source section 6 and shortens the light emitting
period, though overlap of light in adjacent regions is eliminated, but
the light detection amount reduces.

[0066] On the other hand, when the user increases the luminance of the
light source section 6, in connection with the overlap of light in
adjacent regions in the light source section 6, the width of each
overlapped portion changes depending on the shift amount which is
determined by the number of vertical division, and hence the light
detection amount does not become constant. Accordingly, control is
exerted such that all the regions of the light source section 6 emit
light at the timing corresponding to the boundary between the left eye
image and the right eye image.

[0067] FIG. 7 is a timing chart showing the light detection and shutter
switching control. The number of vertical division n of the light source
section 6 is 4, similarly to the example shown in FIG. 6. As shown in
FIG. 7, the timing generation section 2 generates pulses in the light
emission drive signals P1 to P4, to cause all the regions of the light
source section 6 to emit light at the timing corresponding to the
boundary between the left eye image L and the right eye image R
(predetermined period), i.e., around the rising timing of the image
synchronization signal V.

[0068] Further, the timing generation section 2 generates, at the timing
corresponding to the boundary between the left eye image L and the right
eye image R of the image signal I1, which is identical to the timing of
the light detection gate signal GE of the light detection section 4,
pulses in the light emission drive signal Pn for enabling synchronous
light emission. The light emitting period of each pulse of the light
emission drive signal Pn for enabling synchronous light emission is
determined by the sensitivity and light amount of the optical sensors of
the light detection section 4. The period is preferably as short as
possible. For example, it is optimum if it can be set to so short time
that it can be detected by the optical sensors but cannot be sensed by
human eyes. Further, when this light emitting period is increased, it may
overlap with the light emitting period described above. In this case, the
overlap period is permitted because light is emitted.

[0069] Though stable light detection is achieved by exerting control to
cause all the regions of the light source section 6 to emit light at the
same time, because of the light detection, an image in the course of
response of liquid crystal may be shown in the light emitting period of
the light source section 6, whereby 3D crosstalk may appear. Accordingly,
the timing generation section 2 generates, in the light emitting period
of the light source section 6 for light detection, the shutter switching
signals SL, SR for switching the left and right eye shutters to the
non-transmissive mode. Thus, 3D crosstalk is suppressed by the right and
left eye shutters of the shutter glasses section 9 being closed. The
shutter switching signals SL, SR function to allow an image to be
transmissive by opening the shutters in High period; and function to
allow an image to be non-transmissive by closing the shutters in Low
period. The hatched portions in FIG. 7 each represent the period in which
the left and right eye shutters are closed.

[0070] Note that, for example in the case where the left and right eye
shutters of the shutter glasses section 9 are structured with liquid
crystal, the response time may be slow. Taking into consideration of the
response being slow, it is also possible to adjust the rising and falling
timing and High period of the shutter switching signals SL, SR, such that
the left and right eye shutters are fully in the non-transmissive mode at
the timing where all the regions of the light source section 6 emit
light.

[0071] As has been described above, with the stereoscopic image display
device according to the first preferred embodiment, the timing generation
section 2 generates the light emission drive signal Pn for causing all
the regions of the light source section 6 to emit light in a
predetermined period, and generates the light detection gate signal GE
for enabling detection of the light detection section 4. Therefore, the
light detection section 4 can perform detection in the state where all
the regions of the light source section 6 emit light at the same time.
Accordingly, the light detection section 4 can stably perform detection
of the light detection value D with small errors, without being affected
by the amount of light in adjacent regions of the light source section 6.
Since the light source control section 5 controls the light emission
intensity of the light source section 6 based on the light detection
value D with small errors, the illumination color of the light source
section 6 can be maintained to be constant against variations in the
temperature and aging of the light source section 6. Thus, long-term use
of the light source section 6 is realized.

[0072] Further, since the timing generation section 2 generates the
shutter switching signals SL, SR for switching the left and right
shutters to the non-transmissive mode in the predetermined period, by
switching the left and right shutters to the non-transmissive mode in the
period in which all the regions of the light source section 6 are caused
to emit light at the same time, 3D crosstalk attributed to light emission
of the light source section 6 can be suppressed.

[0073] Still further, the light guide section 7 outputting light, which is
received from the light source section 6, to the liquid crystal panel
section 8 is further provided, and the light detection section 4 is
installed between the light guide section 7 and the liquid crystal panel
section 8. Therefore, the light detection section 4 can be installed at
any position between the light guide section 7 and the liquid crystal
panel section 8, and flexibility in installing the light detection
section 4 is enhanced.

[0074] Still further, since the image signal I2 is a signal in which a
black image is inserted between the left eye image L' and the right eye
image R' having undergone conversion with the doubled frame frequency,
the left eye image L' and the right eye image W can be separated from
each other by the black image.

[0075] Note that, since the brightness of the light source section 6
varies depending on the temperature of the light source section 6 itself
and the light emission accumulation time, the reference value recording
section 3 may record and retain the reference light detection value MD
and the reference light emission intensity value ME for each condition,
i.e., the temperature of the light source section 6 and the time having
been elapsed since beginning of use. For example, setting the reference
light emission intensity value ME for each of the cases where the
temperature of the light source section 6 is low and where it is high
brings about the effect of achieving faster convergence to the targeted
color. Further, for example, since the brightness reduces after a lapse
of several years since beginning of use, the reference light detection
value MD may be maintained, to keep the original brightness despite being
applied with voltage. The reference light detection value MD may reduce
in accordance with the light emission accumulation time of the light
source section 6. That is, the reference value recording section 3 may
reduce the value of the reference light detection value MD such that the
targeted brightness is gradually reduced as the time elapses. Thus, the
electric power can be made constant.

[0076] Further, the reference value recording section 3 may record and
retain the light emission intensity value E obtained when the light
source section 6 is turned off, and use the light emission intensity
value E as the initial value of the light emission intensity of the light
source section 6 for the next emission of light. This brings about the
effect of faster convergence to the targeted color. Further, the
reference value recording section 3 may record and retain the reference
light detection value MD and the reference light emission intensity value
ME for each condition, i.e., the white color and the color temperature of
the targeted output light. Thus, the light source section 6 can switch
the setting of color temperature and the like.

[0077] Still further, it has been described that the light emission drive
signal Pn causing the divided regions of the light source section 6 to
emit light at the same time and the corresponding light detection gate
signal GE and shutter switching signals SL, SR are generated for each
frame, and that the light source control section 5 operates to equalize
the light detection value D detected by the light detection section 4
with the targeted reference light detection value MD. However, in the
case where the light emission intensity of the light source section 6
does not vary for each frame, the timing generation section 2 may
generate the light emission drive signal Pn, the light detection gate
signal GE, and the shutter switching signals SL, SR not for each frame
but for each predetermined cycle longer than one frame.

[0078] That is, for example, it is also possible to cause the regions of
the light source section 6, which regions being divided once in several
frames, or every several seconds or minutes, to emit light at the same
time to perform light detection, and to switch the left and right eye
shutters to the non-transmissive mode. Thus, the processes required for
the light source control section 5 to exert control of feeding back the
light detection value D to the light source section 6 can be reduced.

Second Preferred Embodiment

[0079] Next, a description will be given of a stereoscopic image display
device according to a second preferred embodiment. FIG. 8 is a timing
chart showing the light detection and shutter switching control exerted
in the stereoscopic image display device according to the second
preferred embodiment. Note that, in the second preferred embodiment,
identical reference characters are allotted to the constituent elements
similar to those described in connection with the first preferred
embodiment, and the description thereof will not be repeated.

[0080] In the first preferred embodiment, the timing generation section 2
determines the phase shift amount of the light emission drive signal Pn
based on the image synchronization signal V having been determined with
reference to the vertical cycle of the image signal I2. On the other
hand, in the present preferred embodiment, the determination is made with
reference to an image valid signal DE, in place of the image
synchronization signal V.

[0081] The image valid signal DE indicates the period where an actual
image is present in one frame period of the image. In the liquid crystal
panel section 8, synchronous scanning is performed with the image when
the image valid signal DE is in High period, such that a write operation
is carried out. One frame period of the image is equal to the sum of an
image valid period and a blanking period. The blanking period refers to
the period in which no image is written. For example, with a normal
Hi-Vision signal, vertical 1080 lines correspond to the image valid
period, while the total number of lines in the vertical cycle is 1125.
The difference, i.e., 45 lines, corresponds to the blanking period.

[0082] Next, a detailed description will be given of the operation of the
light detection and shutter switching control. As shown in FIG. 8, the
image converting section 1 converts the input image signal I1 such that
the frame frequency is doubled, and inserts one black image between a
left eye image L' and a right eye image R', to generate and output an
image signal I2. Further, an image synchronization signal V indicative of
the head timing of the left eye image L' and that of the right eye image
R' being synchronized with the image signal I2, and an image valid signal
DE are output. Here, High period of the image valid signal DE is the
image valid period, and Low period is the blanking period.

[0083] Further, each wavy line indicates the response of liquid crystal,
and each solid line indicates the light emission drive signal Pn. For the
sake of convenience, it is exemplarily shown that the number of vertical
division n of the light source section 6 is 4. The shift amount S of the
light emission drive signal is determined by the image valid signal DE
and the number of vertical division n of the light source section 6, and
expressed by the following equation. Here, in the following equation, DE
represents the image valid period.

S=DE/n

[0084] In this manner, the falling timing of the light emission drive
signal Pn is time-shifted by the shift amount S. At this time, in order
to indicate the head timing of the left eye image L' and that of the
right eye image R' of the image synchronization signal V, time-shifting
is carried out by the shift amount S with reference to the rising of
image valid signal DE, which is T/2 cycle after the rising of the image
synchronization signal V. In calculating the shift amount S, the image
valid period immediately after the rising of the image synchronization
signal V is not used, and the next image valid period is used.

[0085] Similarly to the first preferred embodiment, pulses for causing all
the regions of the light source section 6 to emit light is generated at
the timing corresponding to the boundary between the left eye image L and
the right eye image R of the image signal I1. More specifically, pulses
for causing all the regions of the light source section 6 to emit light
are generated in the light emission drive signals P1 to P4 around the
rising timing of the image synchronization signal V. Further, at the same
timing, the timing generation section 2 generates pulses in the light
detection gate signal GE, and generates the shutter switching signals SL,
SR for switching the left and right eye shutters to the non-transmissive
mode.

[0086] As has been described above, with the stereoscopic image display
device according to the second preferred embodiment, the timing
generation section 2 determines the shift amount S of the light emission
drive signal Pn with reference to the image valid signal DE and generates
the light emission drive signal Pn. Therefore, the synchronization with
the image write scanning can be achieved more strictly. Further, the
light emission timing of the light source section 6 corresponding to the
response of liquid crystal can be optimized both at the top portion and
bottom portion of the liquid crystal panel section 8, and 3D crosstalk
can be suppressed.

Third Preferred Embodiment

[0087] Next, a description will be given of a stereoscopic image display
device according to a third preferred embodiment. FIG. 9 is a timing
chart showing the light detection and shutter switching control exerted
in the stereoscopic image display device according to the third preferred
embodiment. Note that, in the third preferred embodiment, identical
reference characters are allotted to the constituent elements similar to
those described in connection with the first and second preferred
embodiments, and the description thereof will not be repeated.

[0088] In the first and second preferred embodiments, the image converting
section 1 converts the input image signal I1 such that the frame
frequency is doubled, and inserts one black image between a left eye
image L' and a right eye image R', to generate an image signal I2. The
third preferred embodiment is different from the first and second
preferred embodiments in that, after the frame frequency is doubled, the
same image is inserted twice without inserting any black image.

[0089] As shown in FIG. 9, it is understood that the image signal I1 is an
image in which a left eye image L and a right eye image R from two
eyepoints are sorted to form a pair of left eye image L and right eye
image R in a time-sharing manner. In the case where the image signal I1
is input in order of L1, R1 . . . with one image frame period T, the
image converting section 1 doubles the frame frequency, and thereafter
performs conversion to achieve the order of L1', L R1', R1' . . . with
one image frame period T/2. That is, the image converting section 1
performs the operation of inserting the identical input image twice.

[0090] In connection with the light emission drive signals shown in FIG.
9, each wavy line indicates the response of liquid crystal, and each
solid line indicates the light emission drive signal Pn of the light
source section 6. For the sake of convenience, it is exemplarily shown
that the number of vertical division n of the light source section 6 is
4. For the sake of convenience, it is understood that, in the image
signal I2 being input to the liquid crystal panel section 8, the left eye
image L is a full white image and the right eye image R is a full black
image. When the wavy line rises, the transmittance increases; when the
wavy line lowers, the transmittance reduces. Point C1 is the point where
the write operation of the left eye image L1' corresponding to the area
near the topmost portion of the liquid crystal panel section 8 is
performed with the full-white gray scale level. Though the write
operation of the same L1' image is performed with the full-white gray
scale level after a lapse of T/2 period, the response of liquid crystal
is unchanged because the images are totally identical to each other.

[0091] Point D1 is the point where the write operation of the black image,
which is the next R1' image, is performed. It can be seen that the point
immediately before point D1 is the point where an adequate response time
has elapsed, and where the substantially targeted transmittance
corresponding to the left eye image L1' is achieved. That is, it can be
seen that it is optimum to cause the light source section 6 to emit light
with reference to point D1.

[0092] On the other hand, point C4 is the point where the write operation
of the left eye image L1' corresponding to the upper 3/4 portion of the
liquid crystal panel section 8 is performed with the gray scale level.
Point C4 is shifted rightward in accordance with the lapse of time from
point C1. Point D4 is the point where the write operation of the black
image, which is the next right eye R1' image, at the upper 3/4 portion of
the liquid crystal panel section 8 is performed. It can be seen that, at
the upper 3/4 portion of the screen also, the point immediately before
point D4 is the point where the substantially targeted transmittance
corresponding to the left eye image L1' is achieved.

[0093] In this manner, it is optimum to cause the light source section 6
to emit light with reference to the area near points D1, D2, . . . , Dn.
While the start position of Dn is different from the first preferred
embodiment, the time-shift of the light emission drive signal Pn is
started from the boundary between the left eye image L' and the right eye
image R' of the image signal I2. Similarly to the first preferred
embodiment, the shift amount S of the light emission drive signal Pn is
determined by the cycle T of the image synchronization signal V and the
number of vertical division n of the light source section 6, which is
expressed by the following equation:

S=T/2n

[0094] When T period has elapsed since the rising of the image
synchronization signal V, the falling of the first light emission drive
signal P1 is generated, such that light emission drive signal Pn is
generated as being time-shifted by shift amount S. For example, with the
light source section 6 with four divided regions, the falling point of P1
occurs after a lapse of T period since the rising of the image
synchronization signal V, and the falling point of P2 occurs after a
lapse of T+T/8 period. Note that, similarly to the second preferred
embodiment, the timing generation section 2 may determine the shift
amount S with reference to the image valid signal DE in place of the
image synchronization signal V, and generate the light emission drive
signal Pn.

[0095] The third preferred embodiment is different from the first and
second preferred embodiments in the timing where pulses for causing the
divided regions of the light source section 6 to emit light at the same
time. Since the image converting section 1 does not insert a black image
after the frame frequency is doubled but inserts the same image twice,
the timing generation section 2 generates pulses at the same time for the
light emission drive signals P1 to Pn after a lapse of about T/2 period
since the rising of the image synchronization signal V. Further, the
timing generation section 2 generates pulses for the light detection gate
signal GE and the shutter switching signals SL, SR for switching the left
and right eye shutters to the non-transmissive mode, at the timing
identical to that of the light emission drive signals P1 to Pn.

[0096] As has been described above, with the stereoscopic image display
device according to the third preferred embodiment, the image converting
section 1 doubles the frame frequency and thereafter inserts the same
image twice. Therefore, the time until the liquid crystal fully responds
can be secured, and a reduction in luminance in 3D mode due to slow
response of liquid crystal and crosstalk can be suppressed.

[0097] While the invention has been shown and described in detail, the
foregoing description is in all aspects illustrative and not restrictive.
It is therefore understood that numerous modifications and variations can
be devised without departing from the scope of the invention.